Cavity-back type golf club iron heads include a cavity behind the front face or striking surface of the club head. Typically, the position and overall size and shape of a cavity are selected to remove mass from the club head and/or to adjust the center of gravity of the club head. Such cavity-back iron heads assist a golfer by distributing much of the weight of the golf club head in the perimeter regions of the golf club head, making them more “forgiving” than non-cavity back golf club heads (e.g., traditional “blade” type irons). A golf club head that is more forgiving allows a golf ball to be struck slightly off center on the face of the golf club head with less adverse impact to the distance and/or accuracy of the golf ball flight. Thus, cavity-back type irons are very popular among non-professional and amateur players.
In addition to “forgiveness,” the “feel” of a golf club is important to golfers. Although the “feel” of a golf club results from a combination of various factors (e.g., club head weight, weight distribution, aerodynamics of the club head, weight and flexibility of the shaft, etc.), it has been found that a significant factor that affects the perceived “feel” of a golf club to a user is the sound produced when the golf club head strikes a ball. If a club head makes a strange or unpleasant sound at impact, or a sound that is too loud, such sounds can translate to an unpleasant “feel” in the golfer's mind.
Manufacturers of cavity-back type golf clubs often place a badge or insert in the cavity for decorative purposes and/or for indicating the manufacturer name, logo, trademark, or the like. Additionally, it is known that a badge or insert may be used to achieve vibration and sound damping. Examples of such badges or inserts are disclosed in U.S. Pat. No. 8,920,261 entitled “Badge for Golf Club Head,” assigned to Taylor Made Golf Company, Inc., and incorporated by reference herein in its entirety.
Historically, golf club irons had relatively thicker faces that allowed for relatively smaller amounts of deflection, which resulted in less vibration and sound generation when the face impacts a golf ball. Therefore, badges, inserts or medallions (collectively referred to herein as “badges”) placed behind the front faces of such irons were typically primarily used for decorative design. As the front face of golf club heads have become thinner and their coefficients of restitution (COR) larger, however, the vibration and sound that can be produced when the front face impacts a golf ball has increased. Thus, vibration and sound damping has become more important for such types of golf clubs. For example, for cavity-back golf club iron heads that have relatively thin front faces, vibration and sound damping is desirable to improve the “feel” of the club when the club head impacts the ball.
When placed behind the front striking face of the golf club head for damping purposes, conventional badges damp sounds made from the face of the club vibrating after impact by constraining a layer of viscoelastic material (e.g., VHB Tape) disposed between a rear surface of the face and the badge. The face bends during vibration thereby shearing the VHB tape, which results in damping of the vibration. Generally, the more stiff the badge, the more efficient the viscoelastic layer located between the badge and the rear surface of the face, which improves the sound or feel of the golf club during impact. Stiffness refers to the rigidity of an object and is defined as Force divided by displacement. For purposes of discussion herein, we assume force is fixed. Thus, stiffness (S) can be expressed as a material's elasticity (E) times its area moment of inertia or 2nd moment of area (I). In other words, S=E×I. If we assume that a badge's elasticity remains constant throughout (i.e., the badge has the same material composition throughout) then the stiffness (S) of the badge becomes a function of the badge's area moment of inertia (I).
Although stiff badges are known in the art, such badges are too heavy, which adversely impacts the performance and feel of the club by adversely reducing the coefficient or restitution (COR) and/or increasing the height of the center of gravity (CG) of the club face, for example.
Other types of conventional vibration and sound dampers are typically affixed to the back surface of the face only at the face center (i.e., halfway between the heel and toe). One problem with such damping methods is that placement of the dampers behind the club center face decreases performance of the club head and provides little stiffening to a topline of the club head.